Metallated conjugation in small-sized-molecular donors for solution-processed organic solar cells

Four metallated conjugated oligothiophenes, S-1, S-2, S-3 and S-4, with platinum(II) aryleneethynylenes as the electron-rich building block were synthesized to investigate their physicochemical and photovoltaic properties. These small molecules possess fairly low-lying HOMO energy levels which match with the LUMO energy level of the electron acceptor PC₇₀BM ([6,6]-phenyl-C₇₁-butyric acid methyl ester). Using the simple process of spin-coating solution fabrication technique, S-1:PC₇₀BM (1:4, w/w) based organic solar cells exhibiting a high V _oc of 0.913 V, with a PCE value of 0.88% were developed. In contrast, the OSC device based on S-2:PC₇₀BM (3:7, w/w) displayed a higher PCE of 1.59% with a higher J _sc value of 5.89 mA cm^-2. The device based on S-4:PC₇₀BM (1:4, w/w) exhibited a PCE value of 1.56%, with a V _oc of 0.917 V.